Fixer testing for paper

Had some discussions here about fix testing - I've been using straight hypo for bromoil tests (some claim easier inking vs. rapid) and for Lith (to prevent highlight bleaching). I've been buying small jars of sodium thiosulfate for testing and will order 5 or 10 pounds next time - I've not added sodium sulfite thus far. Small batches of thiosulfate means I've not had a lot of chemistry around.

So after making a round of matrices and fixing post-bleach, I bottled up the plain fixer thinking I might do some more prints that night. Last night - a week or two later - I was playing with Lith and noticed I still had that used fixer and trayed it, but I assumed it was dead without the sulfite.

Some folks on APUG use the film leader test to determine fixer life, others say film-leader doesn't address the differences between fixing paper and film. I just took a strip of paper in room light, bent it so half hung in the fix tray, tested two and three minute strips, and dropped into a graduate with Liquidol (Dektol) 1:9, my standard paper soup. The unfixed halves went straight black, the fixed halves pure white. Even 2 minutes in plain hypo left the paper totally white, so I settled on 3 minutes fixing time. I tested every 3 or 4 prints and the stuff was still good.

I was just using single-bath fixing as well... all I had new was rapid fix, these were just tests, and (I'm assuming) the single bath was doing what it was intended to do, remove the unneeded silver.

Now, my brain clouds up and eyes glaze over when people start saying "well, the silver halides are transmorgified into gluten strands which your test does not address" (love you chemists, but my brain is just full these days I guess). Beyond the science involved, I'm assuming the paper strip test tells me the stuff is doing its job (yet everything I've read says that particular fix batch should be dead by now).

Is my methodology sound and are my assumptions correct? I would be very happy to have such a simple way to determine whether new fix is needed.

Your methodology is sound. I would add a short rinse after the fix and before the developer, and I would make sure that the contaminated developer never gets used as developer for good prints.

But, the fix test for film is just fine for paper. Film just takes longer to fix than paper and so it can give a false time or indication of exhaustion.

And nothing transmogrified! I guarantee it.

PE

This tests activity of your fixer. Is there anything similar that tests whether the fixer has become too saturated with silver?

II understand about the retained silver test for prints, but would like something as cheap and cheerful for us bathroom darkroom folks.

The retained silver test can help with that one Matt. This test will give you an approximate fix time.

PE

I've read in a few places (mainly quite old texts) of testing fixer by mixing with a 5% Potassium iodide solution and looking for precipitate.

Worth doing, or too easily misleading?

Thanks PE - and yes, the cool thing about a strip test is you can put 300ml of dev. in a narrow beaker. (And I did rinse the strips before the dev, figured it kept the results in line with a real workflow).

Regarding the retained silver test - if a strip test says your fixer is chugging along just fine, should one be concerned about silver? Is that to give you an idea of how much life is still probable?

Again, I'm liking a quick test that says "no need to mix more for now", even if I do it every couple prints. Always plenty to do for that 3 minutes.

The Potassium Iodide test is misleading because it is hard to interpret. Also, since papers are low in iodide or contain no iodide, the test will fail.

Retained silver is usually a test for wash quality and thus retained hypo, but it also tells us that the fix step has failed, if the wash step is good.

Basically, aside from the KI test, there are two others. One involves AgNO3 (Silver Nitrate) in Acetic Acid and the other is Na2S (Sodium Sulfide) in water which does not keep well. Either of these two will darken if there is hypo or Silver Halide present and thus they test for fix activity and wash quality if both are done at the end of the entire process.

Myself, I use a blix made by mixing Ferric Ammonium EDTA with the fix. Then I develop a strip in the light which turns it black and dip it in the blix and measure the time to clear. As I use the fix, the time goes up until the strip being tested will not clear. At that point the fixer is dead, but I usually stop using the fixer before then based on the time needed to clear a strip.

And remember, the fix is actually "dead" before any of these tests say it is. It needs an earlier cutoff than these tests indicate.

PE

Photo Engineer said:

And remember, the fix is actually "dead" before any of these tests say it is. It needs an earlier cutoff than these tests indicate.

PE

Click to expand...

That's why I like the simple test of just exposed paper half-dipped; I go by the rule that it's not working after a 3 minute bath, dump it. Though I have found that straight-hypo fixer will prevent paper from going black in 2 minutes or so, significantly longer than the "X number of sheets" in the documentation.

I've ordered the Formulary residual hypo test for a wash test as well, that seems pretty straightforward. I don't expect my stuff to be in a museum in 100 years, but I'd like my prints to last my lifetime (and my kids are really after me for more prints for xmas as well...)

This is a great test for hypo and developer. If it works both are good. If it does not work, then more testing is needed.

You killed one stone with two birds! This is great as it leaves no tern unstoned!

I prefer to leave no tone unsterned. (Ogden Nash's last public comment)

Experimentation and observation will always trump theory.